A variety of devices used in optical systems comprise two or more device components interconnected by optical fiber. For example, a light source, such as a laser, may require a dedicated fiber connection to a polarizer, filter, attenuator, modulator or amplifier. In optical communication systems many applications of such devices, e.g. undersea cable, require an interconnection that is highly reliable and high in optical quality.
A typical interconnected optical device comprises a pair of device components, such as an LED and a filter, interconnected by an optical fiber. The optical fiber comprises a glass optical fiber waveguide typically covered with an outer polymer coating. In the present practice, the polymer coating has a thickness equal to the radius of the glass waveguide, i.e. if r.sub.0 is the radius of the glass waveguide and r.sub.1 is the radius of the coated waveguide, then the coating thickness t=r.sub.1 -r.sub.0. The coated fiber is typically enclosed within a protective capillary tube extending between the device components.
The device is fabricated by bonding and/or soldering at elevated temperatures. The fiber is bonded between the device components at elevated temperature and then permitted to cool to ambient temperature.
A problem that reduces the reliability and quality of interconnected optical devices arises from the tendency of the fiber to buckle within the tube. The material of the tube typically has a higher coefficient of thermal expansion (CTE) than the glass of fiber, with the consequence that after cooling from fabrication at elevated temperature, the fiber is placed under compressive stress. This compressive stress can produce buckling of the fiber within the interior of the tube. The buckling increases the risk of fiber fracture and the induced curvature deteriorates the quality of the fiber as a waveguide. Accordingly, there is a need for interconnected optical devices of enhanced reliability and interconnection quality.